The Human Challenge Core is available to assess the infectiousness of Neisseria gonorrhoeae isogenic mutants developed in this application, or mutants generated by investigators at other CRCs. Specifically, we will examine the requirements for heme and hemoglobin receptors, and requirement for opa proteins. In addition, the Core will test gonococcal isolates that have already been developed as part of the CRC Program. Specifically, mutants less likely to resist the microbicidal action of the neutrophil inflammatory response have been generated. The Core can also support vaccine research, if a vaccine with adequate immunogenicity is developed. Core facilities include the Microbiology laboratory in the Division of Infectious Disease, and the patient care areas of the General research Center.